The function comes in the package `{car}`

in R.

Running some regression models using the `mtcars`

package in R, I can get the VIF both using the function and manually, when the regressor is a continuous variable:

` require(car)`

`## Loading required package: car`

```
attach(mtcars)
fit1 <- lm(mpg ~ wt + hp + disp) # The model we want.
fit_wt <- lm(wt ~ hp + disp) # Regressing wt against other regressors.
rsq_wt <- summary(fit_wt)$r.square # Detecting the R square of the model
(v_wt <- 1/(1 - (rsq_wt))) # Actual formula for VIF
```

`## [1] 4.844618`

` vif(fit1) # R built-in function`

```
## wt hp disp
## 4.844618 2.736633 7.324517
```